Compressor and compressor system

ABSTRACT

A compressor according to an embodiment includes: a discharge valve; a discharge space formed downstream of the discharge valve; a liquid injection hole for injecting a refrigerant liquid into the discharge space; and a heat medium flow path located opposite to the discharge space across a partition wall forming the discharge space.

TECHNICAL FIELD

The present disclosure relates to a compressor and a compressor system.

BACKGROUND

In a compressor, if the compressor is overheated by a compressed gashaving a high temperature and a high pressure, the density of a gas tobe compressed sucked into the compressor decreases, causing a decreasein efficiency of the compressor. Therefore, for example, in areciprocating compressor, as a means for suppressing overheating of thecompressor, a pipe for flowing cooling water is provided inside acrankcase or a head cover. For example, Patent Document 1, 2 discloses aconfiguration for suppressing overheating by injecting a refrigerantliquid into a discharge space in a head cover and cooling a compresseddischarge gas with latent heat of vaporization of the refrigerantliquid.

CITATION LIST Patent Literature

Patent Document 1: JP2010-53765A

Patent Document 2: JP2011-163192A

SUMMARY Technical Problem

According to the configuration disclosed in Patent Document 1, 2, it ispossible to cool the discharge gas, and it is possible to suppressoverheating of the compressor. However, due to an influence of cooling,a large amount of frost may occur on a surface of the compressor (forexample, a surface of the head cover or the casing). Such configurationwhere the large amount of frost occurs is not preferable.

The present disclosure has been made in view of the above-describedproblems, and the object of the present disclosure is to suppresses theoccurrence of frost on the surface of the compressor when the compresseddischarge gas is cooled by injecting the refrigerant liquid into thedischarge space of the compressor.

Solution to Problem

In order to achieve the above object, a compressor according to thepresent disclosure includes: a discharge valve; a discharge space formeddownstream of the discharge valve; a liquid injection hole for injectinga refrigerant liquid into the discharge space; and a heat medium flowpath located opposite to the discharge space across a partition wallforming the discharge space.

Further, a compressor system according to the present disclosure is acompressor system, including: a low-stage compression part; and ahigh-stage compression part. At least the low-stage compression part isconstituted by the compressor as defined in the above.

Herein, the “low-stage compression part” and the “high-stage compressionpart” include a low-stage compressor and a high-stage compressor eachhaving an independent casing, and a low-stage compressor and ahigh-stage compressor housed in a single housing casing, for example, areciprocating compressor.

Advantageous Effects

With the compressor and the compressor system according to the presentdisclosure, since the above-described heat medium flow path is provided,it is possible to increase the temperature of the compressor casingwhich includes the partition wall forming the discharge space, making itpossible to suppress the occurrence of frost on the surface of thecompressor.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a front cross-sectional view of a reciprocating compressoraccording to an embodiment.

FIG. 2 is a system diagram showing a lubricant oil supply system for thereciprocating compressor according to an embodiment.

FIG. 3 is a system diagram showing the lubricant oil supply system forthe reciprocating compressor according to an embodiment.

FIG. 4 is a system diagram of a compressor system according to anembodiment.

DETAILED DESCRIPTION

Some embodiments of the present invention will be described below withreference to the accompanying drawings. It is intended, however, thatunless particularly specified, dimensions, materials, shapes, relativepositions and the like of components described or shown in the drawingsas the embodiments shall be interpreted as illustrative only and notintended to limit the scope of the present invention.

For instance, an expression of relative or absolute arrangement such as“in a direction”, “along a direction”, “parallel”, “orthogonal”,“centered”, “concentric” and “coaxial” shall not be construed asindicating only the arrangement in a strict literal sense, but alsoincludes a state where the arrangement is relatively displaced by atolerance, or by an angle or a distance whereby it is possible toachieve the same function.

For instance, an expression of an equal state such as “same”, “equal”,and “uniform” shall not be construed as indicating only the state inwhich the feature is strictly equal, but also includes a state in whichthere is a tolerance or a difference that can still achieve the samefunction.

Further, for instance, an expression of a shape such as a rectangularshape or a tubular shape shall not be construed as only thegeometrically strict shape, but also includes a shape with unevenness orchamfered corners within the range in which the same effect can beachieved.

On the other hand, an expressions such as “comprising”, “including”,“having”, “containing”, and “constituting” one constitutional elementare not intended to be exclusive of other constitutional elements.

FIG. 1 is a front cross-sectional view of a compressor 10 according toan embodiment, and FIG. 2 is a system diagram showing a lubricant oilsupply system for the compressor 10 according to an embodiment. In FIGS.1 and 2 , the compressor 10 is, for example, a compressor incorporatedin a refrigeration device or the like and configured to compress arefrigerant gas. The compressor 10 includes a discharge valve 12, and adischarge space Sv is formed downstream of the discharge valve 12. Aliquid injection hole 14 for injecting the refrigerant liquid into thedischarge space Sv is formed in a compressor casing 16. In the presentembodiment, as in Patent Documents 1 and 2, a condensate liquid of therefrigerant gas, which is the gas to be compressed, is injected from theliquid injection hole 14 into the discharge space Sv. The condensateliquid evaporates in the high-temperature discharge space Sv, absorbslatent heat of vaporization from a discharge gas Gv, and cools thedischarge gas Gv. Thus, it is possible to suppress overheating of thedischarge gas Gv. However, as the case now stands, frost may occur on asurface of a casing 18 forming the discharge space Sv, as describedabove.

Therefore, in order to suppress the occurrence of frost on the casing18, the compressor 10 includes a heat medium flow path 20 locatedopposite to the discharge space Sv across a partition wall 18 a formingthe discharge space Sv. By flowing a heat medium through the heat mediumflow path 20, the temperature of the casing 18 including the partitionwall 18 a is increased, making it possible to suppress the occurrence offrost on the surface of the casing 18.

In an embodiment, the compressor 10 includes a lubricant oil flow path22 through which lubricant oil r supplied to a part to be lubricatedflows. The heat medium flow path 20 is disposed in series or parallelwith the lubricant oil flow path 22. According to the presentembodiment, since it is possible to cause the lubricant oil r, which hasabsorbed the heat of the part to be lubricated in the compressor 10 bylubricating and cooling the part to be lubricated, to flow through theheat medium flow path 20, the temperature of the casing 18, whichincludes the partition wall 18 a forming the discharge space Sv, can beincreased by potential heat of the lubricant oil r. Therefore, it ispossible to suppress the occurrence of frost on the surface of thecasing 18 of the compressor 10. The part to be lubricated of thecompressor 10 includes, as an example, at least either of a rotor or arotor support portion. As a more specific example, the parts to belubricated are a crank shaft 48 and a thrust bearing 50, which will bedescribed later. The part to be lubricated may be either the crank shaft48 or the thrust bearing 50.

In an embodiment, as shown in FIG. 2 , the heat medium flow path 20 isarranged in series with the lubricant oil flow path 22, and acirculation path 24 for the lubricant oil r including the part to belubricated of the compressor 10, the heat medium flow path 20, and thelubricant oil flow path 22 is formed. Further, the circulation path 24is provided with an oil pump 26 for circulating the lubricant oil r.According to the present embodiment, since the lubricant oil rcirculating in the circulation path 24 by the oil pump 26 is cooled inthe heat medium flow path 20, a dedicated oil cooler is not required anda cost can be reduced.

FIG. 3 shows an embodiment in which the heat medium flow path 20 isdisposed in parallel with the circulation path 24. In the presentembodiment, an oil cooler 28 is provided in the circulation path 24 forthe lubricant oil flowing through the part to be lubricated of thecompressor 10. The lubricant oil r flowing through the circulation path24 flows through the part to be lubricated of the compressor 10, coolsthe part to be lubricated, is heated, and is cooled by the oil cooler28. Further, the compressor 10 includes a branch path 30 branching offfrom the circulation path 24, communicating with the heat medium flowpath 20, and merging with the circulation path 24 again. The lubricantoil r flowing through the branch path 30 exchanges heat with thedischarge gas Gv in the heat medium flow path 20 to heat the dischargegas Gv. According to the present embodiment, since the discharge gas Gvis heated by the heat medium flow path 20, it is possible to suppressfrost generated on the partition wall 18 a or the surface of the casing18 including the partition wall 18 a. Meanwhile, the oil cooler 28 playsthe main role of cooling the lubricant oil r.

As shown in FIG. 3 , the circulation path 24 and the branch path 30 maybe provided with flow control valves 32 and 34, respectively. Only oneof the flow control valve 32 and the flow control valve 34 may beprovided. Since these flow control valves 32 and 34 are provided, it ispossible to control the flow rate of the lubricant oil r flowing throughthe branch path 30, making it possible to control the heating capacityof the heat medium flow path 20. It is preferable that the branchingportion and the merging portion of the branch path 30 with respect tothe circulation path 24 are disposed such that the lubricant oil rhaving a temperature suitable for a heating condition of the heat mediumflow path 20 flows through the heat medium flow path 20.

In an embodiment, as shown in FIGS. 1 and 2 , the compressor 10 is thereciprocating compressor. In this case, the compressor 10 is configuredsuch that a cylinder 40 is housed inside the compressor casing 16 and apiston 42 reciprocates inside the cylinder 40. A valve plate 44 forsupporting the discharge valve 12 is disposed at one end of the cylinder40 (an upper end of the cylinder 40 in the figure) and further, a headcover is provided as the casing 18 which includes the partition wall 18a forming the discharge space Sv. According to the compressor 10 whichis the reciprocating compressor, the temperature of the head coverserving as the casing 18 can be increased by the heat medium flowingthrough the heat medium flow path 20, making it possible to suppress theoccurrence of frost on the surface of the head cover. In the presentembodiment, the casing 18 of the compressor 10 is the head cover, butthe casing 18 is not limited to the head cover. Hereinafter, the casing18 may be called the head cover 18.

Further, as shown in FIGS. 1 and 2 , a crankcase 46 is disposed belowthe compressor casing 16. The crank shaft 48 is supported by thecrankcase 46 via the thrust bearing 50. An oil reservoir Os of thelubricant oil r is formed at the bottom of the crankcase 46. The piston42 is connected to the crank shaft 48 via a connecting rod 52, and thepiston 42 reciprocates inside the cylinder 40 as the crank shaft 48rotates. In the exemplary embodiments shown in FIGS. 1 and 2 , twocylinders 40 are disposed in parallel, and the pistons 42 of the twocylinders 40 are connected to the crank shaft 48 so as to reciprocate inphases different by 180° at a rotation angle of the crank shaft 48.Further, a motor 54 for rotary driving the crank shaft 48 is disposed atone end of the crank shaft 48 outside the crankcase 46. The oil pump 26is disposed at another end of the crank shaft 48 and is operated by therotation of the crank shaft 48.

As shown in FIG. 2 , an oil filter 56 is disposed in the oil reservoirOs, and the oil pump 26 sucks up the lubricant oil r from the oilreservoir Os into the lubricant oil flow path 22. A pressure regulatingvalve 58 disposed at a terminating end of the lubricant oil flow path 522 regulates an oil pressure of the lubricant oil r flowing through thecirculation path 24. The parts to be lubricated, such as the crank shaft48 and the thrust bearing 50, are formed with oil passages 60 and 62.The lubricant oil r discharged from the oil pump 26 to the lubricant oilflow path 22 is supplied to these oil passages. As shown in FIG. 2 , apart of the oil passage 60 is introduced to the piston 42 via a crankpin 53. Further, the lubricant oil r is supplied from the lubricant oilflow path 22 to the heat medium flow path 20 to heat the discharge gasGv. The lubricant oil r that has passed through the heat medium flowpath 20 returns to the oil reservoir Os via the oil passages 60 and 62,or the like. Thus, the circulation path 24 for the lubricant oil rdescribed above is formed.

As shown in FIG. 1 , the suction space Si is formed outside the cylinder40, and if the piston 42 descends and a compression space in thecylinder 40 is decompressed, the refrigerant gas, which is the gas to becompressed, is sucked from the suction space Si into a compression spacein the cylinder 40 through a suction valve 63. The refrigerant gassucked into the compression space is compressed in the compression spaceand discharged to the discharge space Sv. A disc-shaped valve cage 66 ispressed and fixed to an upper surface of the valve plate 44 by a coilspring 64 to block an opening of the valve plate 44. A truncated conicalvalve plate 70 is joined to a lower surface of the valve cage 66 by abolt 68. A discharge gas passage is formed in the valve cage 66 and thedischarge valve 12 is mounted thereon. If the piston 42 rises and a gaspressure in a cylinder chamber increases, the discharge valve 12 ispushed up to discharge the refrigerant gas into the discharge gaspassage.

In an embodiment, as shown in FIGS. 1 and 2 , the compressor 10 includesa coolant flow path 72 for cooling the compressor driving motor 54. Thecoolant flow path 72 communicates with the heat medium flow path 20. Inthe present embodiment, a liquid coolant, which has cooled the motor 54and sucked a potential heat of the motor 54, is flowed through the heatmedium flow path 20 and the casing 18, which includes the partition wall18 a forming the discharge space Sv, can be increased in temperature bypotential heat of the coolant, making it possible to suppress theoccurrence of frost on the surface of the casing 18 of the compressor10.

Furthermore, as another embodiment, for example, heated hot water, anantifreeze liquid, or the like, which is used as a cooling liquid inanother part of the compressor 10, may be supplied to the heat mediumflow path 20 to heat the discharge space Sv.

In an embodiment, as shown in FIG. 1 , a jacket cover 74 internallyhaving a heat medium introduction space is disposed on an outer surfaceof the head cover serving as the casing 18. The heat medium introductionspace forms the heat medium flow path 20. According to the presentembodiment, the heat medium flow path 20 can be formed simply bymounting the jacket cover 74 on the existing compressor and the otherparts do not need modification, making it possible to easily form theheat medium flow path 20.

In the exemplary embodiment shown in FIG. 1 , the jacket cover 74 isformed with an inlet hole 74 a and an outlet hole 74 b of the heatmedium flow path 20, and the lubricant oil flow path 22 is connected tothe inlet hole 74 a and the outlet hole 74 b. Then, the lubricant oil ris supplied from the inlet hole 74 a to the heat medium introductionspace (heat medium flow path 20) and is discharged from the outlet hole74 b to the lubricant oil flow path 22. As shown in FIG. 1 , the inlethole 74 a and the outlet hole 74 b are, respectively, formed at both endportions of the jacket cover 74 away from each other. Thus, it ispossible to increase a residence time of the lubricant oil r in the heatmedium introduction space, and it is possible to improve the heatexchange rate with the discharge gas Gv.

In an embodiment, as shown in FIG. 1 , the liquid injection hole 14 forinjecting the refrigerant liquid into the discharge space Sv includes athrough hole 14 a formed in the valve plate 44, and a communication hole14 b disposed in a wall portion of the compressor casing 16 andcommunicating with the through hole 14 a to cause the through hole 14 ato communicate with an external space. As will be described later, in aheat pump device including the compressor 10, the communication hole 14b is connected to a refrigerant path 76 branching off from anoutlet-side refrigerant path of the liquid receiver 88, and therefrigerant liquid is supplied from the refrigerant path 76 to theliquid injection hole 14.

In an embodiment, as shown in FIG. 1 , one end of the through hole 14 ais open to the discharge space Sv, and another end of the through hole14 a is formed so as to communicate with the communication hole 14 b.

According to the present embodiment, the liquid injection hole 14 can beformed at a position avoiding the head cover 18. If the heat medium flowpath 20 needs to be disposed on the head cover 18 side and the liquidinjection hole 14 is disposed on the head cover 18 side, theinstallation positions of the heat medium flow path 20 and the liquidinjection hole 14 interfere. In the present embodiment, since the liquidinjection hole 14 can be formed at the position on the valve plate 44side avoiding the head cover 18, it is possible to realize a layout ofthe liquid injection hole 14 that can avoid the interference with theheat medium flow path 20.

In the exemplary embodiment shown in FIG. 1 , the communication hole 14b is formed in an upper end portion of the casing surrounding thecylinder 40, which is a part of the compressor casing 16. On the otherhand, the communication hole 14 b may be formed in the valve plate 44.Further, the installation position of the liquid injection hole 14 isnot limited to that of the above embodiment, and may be formed inanother position, for example, in the head cover 18.

In an embodiment, as shown in FIG. 1 , an outer peripheral edge portionof the valve plate 44 is interposed between the compressor casing 16 andan outer peripheral edge portion of the head cover 18. If the outerperipheral edge portion of the valve plate 44 is thus disposed in such amanner as to be exposed to the external space of the compressor 10,processing for opening the liquid injection hole 14 to the externalspace of the compressor 10 is facilitated. Further, as shown in FIG. 1 ,since the outer peripheral edge portions of the compressor casing 16,the valve plate 44, and the head cover 18 are laminated in three layers,the outer peripheral edge portions of these three layers can easily bejoined by fastening together with a bolt 78. Thus, the valve plate 44 ismounted easily.

In an embodiment, a compressor system 80 shown in FIG. 4 is a two-stagecompressor system which includes a low-stage compressor 82 and ahigh-stage compressor 84, and in which the refrigerant gas is the gas tobe compressed, and the low-stage compressor 82 is constituted by thecompressor 10 according to the above embodiment. Since the low-stagecompressor 82 is constituted by the compressor 10, it is possible tosuppress the occurrence of frost on the surface of the casing 18, whichincludes the partition wall forming the discharge space, in thelow-stage compressor 82.

In the exemplary compressor system 80 shown in FIG. 4 , the low-stagecompressor 82 and the high-stage compressor 84 are each constituted bythe reciprocating compressor. A liquid receiver 88 is disposed on arefrigerant circulation path 86, and the refrigerant liquid in theliquid receiver 88 is decompressed by an expansion valve 90 through therefrigerant circulation path 86, and evaporates by absorbing latent heatof vaporization from a load in an evaporator 92. The refrigerant gasevaporated in the evaporator 92 is sucked into a suction chamber 94 ofthe low-stage compressor 82, is further sucked into a cylinder 98 via asuction valve 96, and is compressed.

The refrigerant gas compressed by the cylinder 98 is discharged to adischarge chamber 102 via a discharge valve 100 and discharged from thedischarge chamber 102 to the refrigerant circulation path 86. Therefrigerant gas discharged to the refrigerant circulation path 86 issucked into the suction chamber 94 of the high-stage compressor 84 afterthe lubricant oil is separated by an oil separator 104. The refrigerantgas sucked into the suction chamber 94 of the high-stage compressor 84is further sucked into the cylinder 98 via the suction valve 96, iscompressed, and is discharged from the discharge chamber 102 to therefrigerant circulation path 86. The refrigerant gas discharged to therefrigerant circulation path 86 is cooled and liquefied by the condenser106 after the lubricant oil is separated by the oil separator 104.

A branch path 108 branching off from the refrigerant circulation path 86is disposed downstream of the liquid receiver 88, and the branch path108 is provided with a liquid pump 110 and a pressure regulating valve112. The branch path 108 is connected to the discharge chamber 102 ofthe high-stage compressor 84, and the refrigerant liquid is pressurizedto have a higher pressure than the discharge chamber 102 of thehigh-stage compressor 84 by controlling a rotation speed of the oil pump26 and the pressure control with the pressure regulating valve 112, andis injected into the discharge chamber 102 from an injection nozzle 114disposed in the discharge chamber 102. The injected refrigerant liquidevaporates under the temperature and pressure conditions of thedischarge chamber 102 to cool the discharge space.

Further, the refrigerant circulation path 86 is provided with a branchpath 116 branching off from the refrigerant circulation path 86 at adownstream position of the branch path 108. The branch path 116 isconnected to the injection nozzle 114 disposed on an inner wall surfaceof the discharge chamber 102 of the low-stage compressor 82. Since thedischarge chamber 102 of the low-stage compressor 82 has the lowerpressure than the branch path 116, the refrigerant liquid can besupplied to the discharge chamber 102 at the same pressure withoutincreasing the pressure. The discharge chamber 102 of the low-stagecompressor 82 is cooled by evaporation of the refrigerant liquidinjected from the injection nozzle 114 under the temperature andpressure conditions of the discharge chamber 102. In the presentembodiment, since the low-stage compressor 82 is constituted by thecompressor 10 according to each of the above-described embodiments, itis possible to suppress frost generated on the surface of the casing(head cover) 18 of the compressor 10.

In the compressor system 80 shown in FIG. 4 , the low-stage compressor82 and the high-stage compressor 84 may constitute a single-machinetwo-stage compressor in which the low-stage compressor and thehigh-stage compressor are housed in one casing. For example, in thecompressor 10 shown in FIG. 1 , a compressor system may be configured inwhich one cylinder 40 is the low-stage compressor and the anothercylinder is the high-stage compressor.

The contents described in the above embodiments would be understood asfollows, for instance.

1) A compressor (10) according to one aspect includes: a discharge valve(12); a discharge space (Sv) formed downstream of the discharge valve; aliquid injection hole (14) for injecting a refrigerant liquid into thedischarge space; and a heat medium flow path (20) located opposite tothe discharge space across a partition wall (18 a) forming the dischargespace.

With such configuration, since the above-described heat medium flow pathis provided, it is possible to increase the temperature of thecompressor casing which includes the partition wall forming thedischarge space, making it possible to suppress the occurrence of froston the surface of the compressor.

2) A compressor according to another aspect is the compressor as definedin 1), including: a lubricant oil flow path (22) through which lubricantoil (r) supplied to a part to be lubricated of the compressor flows. Theheat medium flow path (20) is disposed in series or parallel with thelubricant oil flow path (22).

With such configuration, since it is possible to cause the lubricantoil, which has been used to lubricate the part to be lubricated of thecompressor and absorbed the heat of the part to be lubricated, to flowthrough the heat medium flow path, the temperature of the partition wallforming the discharge space can be increased by potential heat of thelubricant oil. Therefore, it is possible to suppress the occurrence offrost in the compressor casing including the partition wall.

3) A compressor according to still another aspect is the compressor asdefined in 2), wherein the heat medium flow path is arranged in serieswith the lubricant oil flow path such that a circulation path (24) forthe lubricant oil including the part to be lubricated, the lubricant oilflow path (22), and the heat medium flow path is formed, and wherein thecompressor comprises an oil pump (26) for circulating the lubricant oilin the circulation path.

With such configuration, since the lubricant oil flowing through thelubricant oil circulation path exchanges heat with the discharge gas inthe heat medium flow path and is cooled by the discharge gas, the heatmedium flow path doubles as an oil cooler. Therefore, a dedicated oilcooler is not required, making it possible to reduce a cost.

4) A compressor according to yet another aspect is the compressor asdefined in any one of 1) to 3), including: a compressor driving motor(54); and a coolant flow path (72) for cooling the compressor drivingmotor. The coolant flow path communicates with the heat medium flow path(20).

With such configuration, since the coolant for cooling the compressordriving motor flows though the heat medium flow path, the temperature ofthe compressor casing which includes the partition wall forming thedischarge space can be increased by potential heat of the coolant thathas cooled the compressor driving motor and absorbed heat, making itpossible to suppress the occurrence of frost on the surface of thecompressor.

5) A compressor according to yet another aspect is the compressor asdefined in any one of 1) to 4), including: a compressor casing (16); acylinder (40) disposed in the compressor casing; a piston (42) forreciprocating inside the cylinder; a valve plate (44) disposed at oneend of the cylinder and configured to support the discharge valve; and ahead cover (18) which includes the partition wall (18 a) forming thedischarge space.

With such configuration, the temperature of the above-described headcover can be increased by the heat medium flowing through the heatmedium flow path, making it possible to suppress the occurrence of froston the surface of the head cover.

6) A compressor according to yet another aspect is the compressor asdefined in 5), including: a jacket cover (74) disposed on an outersurface of the head cover and internally having a heat mediumintroduction space. The heat medium introduction space forms the heatmedium flow path (20).

With such configuration, the heat medium flow path can be formed simplyby mounting the above-described jacket cover on the existing compressorand the other parts do not need modification, making it possible toeasily form the heat medium flow path.

7) A compressor according to yet another aspect is the compressor asdefined in 5) or 6), wherein the liquid injection hole (14) includes: athrough hole (14 a) formed in the valve plate (44); and a communicationhole (14 b) disposed in a wall portion of the compressor casing (16) andcommunicating with the through hole (14 a) to cause the through hole (14a) to communicate with an external space.

With such configuration, since the heat medium flow path needs to bedisposed on the head cover side and the liquid injection hole is formednot on the head cover side but on the valve plate side, it is possibleto avoid interference with the heat medium flow path and it is possibleto realize the layout of injection hole.

8) A compressor according to yet another aspect is the compressor asdefined in any one of 5) to 7), wherein an outer peripheral edge portionof the valve plate (44) is interposed between the compressor casing (16)and an outer peripheral edge portion of the head cover (18).

With such configuration, the outer peripheral edge portions of thecompressor casing, the valve plate, and the head cover are fastenedtogether with a fastener such as a bolt, making it easier to install thevalve plate. Further, since the end face of the outer peripheral edgeportion of the valve plate is exposed to the external space, it is easyto form the liquid injection hole through which the discharge space andthe external space communicate with each other.

9) A compressor system (80) according to one aspect is a compressorsystem (80), including: a low-stage compression part (82); and ahigh-stage compression part (84). At least the low-stage compressionpart (82) is constituted by the compressor (10) as defined in any one of5) to 8).

With such configuration, since the low-stage compression part isconstituted by the compressor according to each embodiment, it ispossible to suppress the occurrence of frost on the surface of thecompressor in the low-stage compression part.

REFERENCE SIGNS LIST

-   -   10 Compressor    -   12, 100 Discharge valve    -   14 Liquid injection hole    -   14 a Through hole    -   14 b Communication hole    -   16 Compressor casing    -   18 Casing (head cover)

18 a Partition wall (partition wall forming discharge space)

20 Heat medium flow path

22 Lubricant oil flow path

24 Circulation path

26 Oil pump

28 Oil cooler

30, 108, 116 Branch path

32, 34 Flow control valve

40, 98 Cylinder

42 Piston

44 Valve plate

46 Crankcase

48 Crank shaft

50 Thrust bearing

52 Connecting rod

53 Crank pin

54 Compressor driving motor

56 Oil filter

58 Pressure regulating valve

60, 62 Oil passage

63, 96 Suction valve

64 Coil spring

66 Valve cage

68, 78 Bolt

70 Valve plate

72 Coolant flow path

74 Jacket cover

74 a Inlet hole

74 b Outlet hole

76 Refrigerant path

80 Compressor system

82 Low-stage compressor

84 High-stage compressor

86 Refrigerant circulation path

88 Liquid receiver

90 Expansion valve

92 Evaporator

94 Suction chamber

102 Discharge chamber

104 Oil separator

106 Condenser

110 Liquid pump

112 Pressure regulating valve

114 Injection nozzle

Gv Discharge gas

Os Oil reservoir

Si Suction space

Sv Discharge space

r Lubricant oil

1. A compressor, comprising: a discharge valve; a discharge space formeddownstream of the discharge valve; a liquid injection hole for injectinga refrigerant liquid into the discharge space; and a heat medium flowpath located opposite to the discharge space across a partition wallforming the discharge space.
 2. The compressor according to claim 1,comprising: a lubricant oil flow path through which lubricant oilsupplied to a part to be lubricated of the compressor flows, wherein theheat medium flow path is disposed in series or parallel with thelubricant oil flow path.
 3. The compressor according to claim 2, whereinthe heat medium flow path is arranged in series with the lubricant oilflow path such that a circulation path for the lubricant oil includingthe part to be lubricated, the lubricant oil flow path, and the heatmedium flow path is formed, and wherein the compressor comprises an oilpump for circulating the lubricant oil in the circulation path.
 4. Thecompressor according to claim 1, comprising: a compressor driving motor;and a coolant flow path for cooling the compressor driving motor,wherein the coolant flow path communicates with the heat medium flowpath.
 5. The compressor according to claim 1, comprising: a compressorcasing; a cylinder disposed in the compressor casing; a piston forreciprocating inside the cylinder; a valve plate disposed at one end ofthe cylinder and configured to support the discharge valve; and a headcover which includes the partition wall forming the discharge space. 6.The compressor according to claim 5, comprising: a jacket cover disposedon an outer surface of the head cover and internally having a heatmedium introduction space, wherein the heat medium introduction spaceforms the heat medium flow path.
 7. The compressor according to claim 5,wherein the liquid injection hole includes: a through hole formed in thevalve plate; and a communication hole disposed in a wall portion of thecompressor casing and communicating with the through hole to cause thethrough hole to communicate with an external space.
 8. The compressoraccording to claim 5, wherein an outer peripheral edge portion of thevalve plate is interposed between the compressor casing and an outerperipheral edge portion of the head cover.
 9. A compressor system,comprising: a low-stage compression part; and a high-stage compressionpart, wherein at least the low-stage compression part is constituted bythe compressor according to claim 5.